A superbug may be lurking in the remote corners of your MRI or CT unit. Unless you adopt a rigorous cleaning regime, it could pose a grave risk to patients, according to new research from Ireland. Along with those in the U.K. and Malta, hospitals in Ireland have the highest incidence rate of methicillin-resistant Staphylococcus aureus (MRSA) infections in Europe. This prompted a team from Dublin's Mater Misericordiae Hospital to investigate whether they could find the superbug in their radiology department.

An infection control nurse identified high-risk areas in the department, which performed 144,000 radiological examinations during 2004. In total, 125 Copan albumin swabs were taken and analysed for MRSA in the microbiology department using oxycillin culture media. The only positive specimen came from the bore of the MR system.

"This is a difficult area to clean satisfactorily," said radiologist Dr. Timothy Scanlon, lead author of the scientific poster presented at the RSNA meeting. "After evaluating cleaning methods, a special long-handled extended cleaning tool lubricated with hyperchlorite anti-MRSA cleaning agent was used in a circular mode to sterilize the magnet bore. Ten days later, a repeat swab was negative."

S aureus readily grows on human skin and mucous membranes. MRSA is a strain of S aureus that is resistant to semisynthetic penicillins and all beta-lactam antibiotics, making it multiply resistant. It is usually transmitted from patient to patient via the hands of healthcare workers following direct contact.

Colonized and infected patients are the main reservoirs of MRSA, but it has also been found on floors, sinks, work areas, tourniquets used for blood drawing, and blood pressure cuffs. Once it becomes endemic, it is rarely eliminated and may eventually account for up to half of all nosocomial Staphylococcal infections.

Data from the European Antimicrobial Surveillance System show that 42% of S aureus bacteremia cases in Ireland in 2003 were caused by MRSA. During the same year, the U.K. had the highest number of cases of MRSA at nearly 160 per million population, followed by Malta at around 140 and Ireland at 135. The problem is also growing in Israel, Portugal, Luxembourg, Spain, Austria, and Croatia.

"Despite the high incidence of MRSA in Ireland, the point prevalence of the superbug within our radiology department was almost entirely negative," Scanlon said. "Our standard control measures are adequate."

Scanlon advises radiologists to make sure the correct cleaning substance (i.e., a hyperchlorite anti-MRSA microbial agent) is used. He recommends introducing a regular biannual screening program to ensure detection and monitoring of MRSA, as well as having strict handwashing and glove-wearing policies.